Apparatus for turning truss jig



March 4, 1969 J, D. ADAMS 3,430,943

APPARATUS FOR TURNING TRUSS JIG Filed Jun 26, 1967 Sheet of 2 INVENTOR JAMES D. ADAMS ATTORNEY March 4, 1969 J. D. ADAMS APPARATUS FOR TURNING "muss JIG Sheet ,2 bra Filed June 26, 1967 mm m WA w 0 S E M m ATTORNEY United States Patent 6 Claims ABSTRACT OF THE DISCLOSURE A chain drive and fluid motor drive is combined to turn a flop-over roof truss jig from a horizontal position to a position 180 horizontally therefrom, and to provide a braking or cushioning action during the operation of turning over the jig. The fluid motor drive coacts with a chain drive to start the pivoting action of the truss jig, and both provide for moving the truss jig from a horizontal to a vertical position. From the vertical position to either horizontal position the cylinders act as shock absorbers or brakes to ease the jig down to the horizontal position.

This application is an improvement over copending application Ser. No. 374,720, by Carl Junk, filed June 12, 1964, now Patent 3,332,679 for Roof Truss Jig, and assigned to the assignee of the present invention. In said copending application there is described and claimed a truss jig of the pivotal type. Such jigs have been variously called trunnion jigs, flop-over jigs, flip-flop jigs, reversing jigs, etc. A main feature of such jigs is a horizontally disposed table or frame for holding the individual timber members or components of roof or other types of wooden trusses in proper position during manufacture so that the individual wooden members may be secured together, usually by gusset plates at the joints. It is highly desirable to utilize gusset plates on both sides of every joint. The usual jig is a horizontal table or frame and after the gusset plates are applied to the joints of the members on one side, the table or frame is turned over to expose the opposite sides of the joints for applying gusset plates thereto. Most prior art jigs use a trunnion bar on the base or lower chord of the truss, and the remaining components of the jig extend outwardly on one side from the trunnion bar. Roof trusses are normally triangular shaped, with the apex at a substantial distance away from the chord or the trunnion bar. The entire weight of the truss and the supporting members of the jig table or frame extends outwardly from the trunnion bar. This creates a high moment, and a very high torque is required to turn the truss and the jig table from one horizontal position to the turned over horizontal position. Lever arms and/or sprockets attached to the trunnion bar, for turning the jig table, must be of a limited size due to the geometry which requires the truss chord to be placed closely adjacent to the trunnion bar. In the above-identified copending application a hydraulic actuated motor-chain drive operates generally satisfactorily for smaller trusses, but as trusses increase in size the stresses on the jig mechanism also increase above tolerable limits.

According to the present invention the combination of an electric motor chain drive and fluid cylinders is utilized for easily and effectively turning a jig table from one horizontal position to an opposed horizontal position, providing power actuating means for moving the jig table from one horizontal position to a vertical position and then provide a braking power for the jig table as it pivots down to a horizontal position. In one form, the power stroke of a pair of air cylinders attached to a bell crank on either side of a chain drive mechanism aids the turning of the jig table from a horizontal to a vertical position, and then by slowly bleeding air from the cylinder, the piston acting against the air cushions and brakes the pivotal movement of the jig table in its movement from a vertical to a horizontal position.

Included among the objects and advantages of the present invention is a combined drive mechanism for turning a roof truss jig table from one horizontal position to the opposite horizontal position etfectively and smoothly.

Another object of the invention is to provide a drive system for the turning mechanism of a roof truss jig table which has reduced power requirements for turning heavy jig tables from one horizontal position to the other.

A still further object of the invention is to provide a drive system for turning a jig table for a roof truss which combines an electric motor-chain drive with a fluid motor, which fluid motor aids table movement, in its power stroke, from a horizontal position to a vertical position of the jig table and provides cushioning and braking action in lowering the jig table from the vertical to a horizontal position.

These and other objects and advantages of the invention may be readily ascertained by referring to the following description and appended illustrations in which:

FIG. 1 is a perspective view of a jig table for wooden roof trusses, illustrating the main housing and power unit for turning the jig table from one horizontal position to another horizontal position on the opposite side of the housing;

FLIG. 2 is a perspective view, partially cut away, and partially exploded, showing the positioning of the electric motor-chain drive and one fluid cylinder for rotating the trunnion bar of a jig table, according to the invention; and

FIG. 3 is a schematic view of a power cylinder and its positioning in turning the jig table from one horizontal position to the opposed horizontal position.

In the device selected for illustration in the drawings, a central housing 10 provides an enclosure for the electric motor drive, control members and, also, provides a support for a trunnion bar 11, mounted on pillow blocks 12 mounted on the housing 10. Central support arms 13 for timber clamps 14 extend normally from the center of the trunnion bar 11 and provide means for clamping the apex joint of a triangular shaped wooden truss. The housing 10 provides a block 15 for supporting the arms 13 in a substantially horizontal position. The general arrangement of the components of such a jig table is shown in the above-identified copending patent application, and these include trunnion bar extensions 17 and 18 which extend outwardly from either side of the central trunnion bar 11. Clamp support single bars 20 and 21 are adjustably mounted on the trunnion bar extensions 17 and 18, respectively, and two clamp frames 24 and 25 are mounted on the extension 17, and on the opposite side extension 18, clamp supports 28, 29 and 30 are mounted. Clamp supports 20a and 21a are mounted on the supports 20 and 21, respectively. End supports 33 and 34 provide pivotal support for the ends of the extension bars 17 and 18, respectively, for permitting the trunnion bar to turn with support at its ends.

Mounted in the housing is an electric motor 40 with an attached gear reducer 41, mounted on a power drive base 42 retained in position by braces 43. A chain drive 44 extends from a sprocket mounted on the shaft of the gear reducer to a sprocket 45 mounted on a shaft 46 which is held in place by bearing blocks 47 mounted on the sides of the housing. The diameter of the driven sprocket.45 is quite large in relation to the diameter of the drive sprocket to give a large mechanical advantage. A pair of sprockets 48 and 49 are mounted on the trunnion bar 11, and chains 50 and 51 mounted on the sprockets 49 and 48, respectively, are, also, mounted over sprockets 52 and 53. The sprockets 52 and 53 are driven by the sprocket 45, with all said sprockets being keyed to the shaft 46. The motor 40 is a reversible motor and provides means for turning the trunnion bar 180 and reverse. A limit switch 55 and a limit switch 56 mounted adjacent the chain drive 44, with an appropriate stop 56 mounted on a sprocket 45 permits the chain 44 to move a limited distance and thereby provides a limit on the pivoting of the jig table, from one horizontal position to the other horizontal position which is about 180.

To aid the movement of the jig table, a fluid actuated cylinder is mounted on each side of the housing, and the one shown in FIG. 2 includes a cylinder 60 which is pivotally mounted on a cylinder support bracket 61 by means of a pivot pin 62. A connecting link 63 connects a piston shaft 64 of the cylinder with a link 65 which is pivotally connected to a bell crank arm 66 mounted on the trunnion shaft 11 and arranged to be keyed thereto. The bell crank 66 is connected to the link by means of a pivot pin 67 to permit free movement therebetween. A similar cylinder arrangement is mounted on the pposite side of the housing and is connected to the opposite end of the central trunnion bar 11. A time delay relay 70 controls a relay switch 71 for operating the fluid valve to the cylinder 60. The use of a time delay relay for actuating the relay switch will be explained below during the operation of the device. As explained in the aboveidentified copending application, a control switch stand with a power cable to the housing is provided for operating the motor and the solenoid valves in the air line to the cylinders. Such a control stand is merely a switch box with a long lead or power cord which permits the operator to stand in various positions for the operation of the machine.

Various switches for operating the clamps on the jig and conventional regulating valves, pressure gauges and the like are, of course, required for the control of the unit for the electrical and air systems. Such control devices are conventional and have been deleted from the drawing for simplicity; however, it is understood that these are mounted in the housing along with the equipment shown.

For operation of the device, after the timbers for the truss have been placed in position and the clamps locked on the timbers to hold them in position, gusset plates are applied to the exposed joints, normally at the clamp areas of the jig. The gusset plates may be applied with nails or the like to hold them in position. Many gusset plates have teeth pressed out of them and gusset is held in place by nails until the toothed gusset plate is pressed into the wood. When gusset plates are applied to each of the joints on the one side, the controls are actuated to pivot the table so that it flops over, exposing the opposite sides of the joints for application of the gusset plates. As shown in FIG. 3, the jig table, illustrated by the central bars 13, is in the left-hand position A, with the piston rod fully extended to the end 60a of the cylinder. When an operator actuates the switch, starting the motor 40, air is, also, introduced into the head and 60a of the cylinder to force the piston toward the head end 60b. Air under pressure is applied until the piston reaches position B, where the jig table is in vertical position, as by position B of the lateral arms 13. In this position the piston rod is fully retracted into the cylinder 60. At this point the air is cut off and the time delay relay is actuated to permit a short delay in opening a bleed valve in the air line. The motor continues to turn, rotating the arms toward position C, which is the opposite horizontal position of position A; after the short delay and when the arms 13 are at an angle to the vertical and moving toward the horizontal, the relay 71 is closed by the time delay relay 70 to thereby open a bleed valve so that air is gradually bled from the cylinder as the piston extends to position C. In this manner the weight of the truss and the jig is cushioned against the air in the cylinder, which is slowly bled to permit the jig to move down to position C under the braking action of the cylinders on each side of the housing. For returning the table to position A from position C after the completed truss has been removed, the cylinders may not be necessary; however, in the event the weight of the jig is greater than the motor can smoothly and easily handle, the sylinders may be used to aid the motor in pulling up the jig table to vertical position B, and the time delay relay subsequently opens the bleed valve to permit the weight of the jig table to be cushioned against the air in the cylinder, which is slowly bled from the end 60a, till the table is returned to position A. At this original position, more truss components are placed on the jig, the clamps actuated and the process repeated.

In the device illustrated, a single acting air cylinder provides power and cushioning for the turning of the jig table from one horizontal position to the other; however, other fluid cylinders may be used, such as double acting cylinders, hydraulic cylinders, etc. For hydraulic cylinders, proper hydraulic lines for the passing of fluid to and from the cylinder are necessary, and a similar bleed valve may be used to provide a hydraulic cushion for the table in its operation. Further, a chain drive has been shown, since this is found to be an effective drive with high multiplication, and with the air cylinders a much smaller motor can be used than would normally be re quired for the load encountered by the trunnion bar.

While the invention has been illustrated by reference to a particular embodiment, there is no intent to limit the spirit or the scope of the invention to the precise details so set forth except as defined in the following claims.

I claim:

1. Apparatus for turning a jig table for roof truss componets during manufacturing comprising a housing for supporting a jig frame including a bar pivotally mounted on said housing; at least a pair of sprockets mounted on said bar for pivoting the same; means inclusive of drive means connected with and arranged for rotating said sprockets for pivoting said bar and said jig table from one horizontal position through about to the opposite horizontal position and return the same to original position; at least one crank arm mounted on said bar adjacent said housing, a fluid activated cylinder and piston assembly mounted on said housing and attached to said crank arm in position so that movement of its piston helps move said jig table from a horizontal position to vertical position; fluid line means for supplying fluid under pressure to said cylinder for cooperatively moving said jig table from a horizontal to vertical position with said drive means; and means inclusive of a timing means for controlled release of fluid from said cylinder when said jig table moves from vertical to a horizontal position.

2. Apparatus according to claim 1 wherein said drive means is a reversible electric motor connected by a chain drive to an intermediate shaft and a pair of drive sprockets mounted on said intermediate shaft are connected by chain drives to said at least a pair of sprockets.

3. Apparatus according to claim 1 wherein a pair of crank arms are mounted on said bar and a pair of cylinders are connected thereto.

4. Apparatus according to claim 1 wherein limit switches are mounted on one of said sprockets for limiting movement thereof to about 180 rotation.

5 Apparatus according to claim 1 wherein said cylinder is positioned with its piston extended in either horizontal position and retracted in vertical position.

6. Apparatus according to claim 5 wherein said bar is mounted at one side of said housing and a pair of crank arms are mounted on said bar at a position spaced from said housing, and a pair of cylinders are mounted on and externally of said housing with the piston rods of each attached to the respective crank arm.

References Cited UNITED STATES PATENTS 1,112,627 10/1914 Kneedler 60-57 2,186,113 1/1940 Laabs 60-6 3,332,679 7/1967 Junk 269-58 3,371,921 3/1968 Hollomon 26925 ROBERT C. RIORDON, Primary Examiner.

D. R. MEITON, Assistant Examiner.

US. Cl. X.R. 

